Borehole expandable tubular drilling technology is one of the effective techniques to ensure the stability of borehole wall in complex formation. In this paper， a self-tensioning expandable tubular wall protection method is proposed for the strong water-sensitive strata prone to shrinkage， collapse and falling block. According to the wall protection principle of the method， a new type of reaming drill tool， expandable tubular and expandable tubular delivery device are developed to adapt to this method. Local reaming can be carried out on complex hole sections without changing the drilling structure. The delivery expansion tube naturally springs open with its own tension and is fixed in the corresponding reaming section to realize wall protection during drilling. The machine was optimized through indoor and field tests， and finally achieved good application results. The tests proved that： The method is simple， reliable and easy to locate. Compared with cement slurry wall protection， it has the advantages of fast processing speed， short stop time and less repeated processing. It is suitable for the solid wall and wall protection of complex formation in porous section in core drilling field， which is conducive to reducing the cost of in-hole accident treatment and improving drilling efficiency， and has good application value.